The present invention relates to a turbine engine component and the method by which it is made.
In making components for turbine engines, airfoils or vanes have been made separately from shrouds to which they are subsequently attached. It is well known that the strength and corrosion resistance of these airfoils can be enhanced by having the grain boundaries oriented parallel to the longitudinal axes of the airfoils, that is, perpendicular to the direction of gas flow across the airfoils.
In the past, the shrouds of turbine engine components have been cast with a fine, equiaxed grain structure. These shrouds have substantially uniform metallurgical properties in every direction. However during operation of a turbine engine, the forces to which the shrouds are subjected are usually greater in one direction than another direction.
It is also a known practice to form inner and outer shrouds from a plurality of sections. When this is done, opposite ends of an airfoil are connected to a pair of shroud sections. The various pairs of shroud sections are then interconnected to form a turbine engine component having an annular array of airfoils disposed between a pair of circular shrouds. When this practice is being followed, difficulty may be encountered in maintaining the shroud sections in the desired relationship with each other while an airfoil is connected with the shroud sections.
Difficulties have also been encountered in casting arcuate sections of the shrouds integrally with the airfoils. By directional solidification techniques, it has been possible to produce an elongated columnar grain structure extending parallel to the longitudinal axes of the airfoils when they are cast integrally with the shroud sections. However, the grains in the shroud sections are oriented perpendicular to the major side surfaces of the shroud sections. This results in the grain ends in the shrouds being exposed to the flow of hot gases through the turbine engine component.